Specialized transducing phages derived from lambda or phi 80 and carrying bacterial genes coding for certain E. coli membrane proteins have been constructed. The genes for the membrane proteins are brought into proximity to the phage integration site by selection for fusion of two episomes, each carrying the respective locus. This method has been employed for genes involved in the transport of lactose, potassium, beta-glucosides, hexose-phosphates and several amino acids. The synthesis of these proteins following viral replication in lysogenic cells will be assayed by changes in cellular transport activity and by electrophoresis of the cytoplasmic and membrane proteins obtained from isotopically labeled cells. Control cells will be those lysogenic for a similar phage lacking the specific membrane protein. The cellular location of the amplified membrane protein will be measured in this way. If a portion of the protein remains soluble, its purification will be attempted. Its interaction with cellular and synthetic membranes can then be assayed by binding to membranes and by restoration of transport function.